The present invention relates to refrigeration systems and, more specifically, to a modular refrigeration system utilizing a low charge hydrocarbon refrigerant.
A refrigerated merchandiser is generally known in the art. A refrigerated merchandiser is used by grocers, convenience stores, or other sellers of food items to store and display food items within a predetermined temperature range. Refrigerated merchandisers may employ different refrigerants to maintain the predetermined temperature range. Examples of refrigerants may include, but are not limited to, hydrofluorocarbons (HFC), perfluorocarbons (PFC), HFC blends (including R-404A and R-407A), ammonia, carbon dioxide, and hydrocarbons.
Unlike inert refrigerants, hydrocarbon refrigerants have additional government regulations due to flammability and/or toxicity. Typically, regulations focus on limiting the quantity of hydrocarbon refrigerant in a single refrigeration circuit. For example, propane is an approved hydrocarbon for use as a refrigerant in certain applications, including commercial refrigerated merchandisers. However, the Environmental Protection Agency (EPA) regulates the amount of propane which may be used to charge a single refrigeration circuit. For example, the EPA typically limits the refrigerant charge in a refrigeration circuit to 150 grams or less of propane refrigerant. This is for safety purposes in order to limit the potential for a dangerous ignition should the propane refrigerant leak from the refrigeration circuit.
In order to meet commercial refrigeration demands while also complying with hydrocarbon charge regulations, a single commercially available refrigerated merchandiser will typically employ a plurality of refrigeration circuits that operate in parallel. Each refrigeration circuit will have a refrigeration charge of no more than 150 grams of hydrocarbon refrigerant. The refrigeration circuits cooperatively operate to provide a desired amount of refrigeration.
However, refrigerated merchandisers employing a plurality of refrigeration circuits have certain undesirable characteristics. For example, additional components are necessary to operate each of the separate refrigeration circuits. The additional components may include, but are not limited to, additional piping, compressors, condensers, and control technology to achieve a desired amount of refrigeration in the merchandiser. These additional components not only increase initial costs of constructing refrigerated merchandiser systems, but typically lead to higher maintenance costs to maintain the additional components over the life of the systems. Also, the parallel refrigeration circuits in commercially available merchandisers do not maximize cooling load. Instead, the total amount of hydrocarbon refrigerant associated with the merchandiser is increased. So while each refrigeration circuit complies with government regulations, the total amount of hydrocarbon refrigerant associated with the merchandiser exceeds 150 grams, and typically is between 150 and 600 grams.